1. Field of the Invention
The invention is generally related to equipment used in the offshore drilling and production industry to handle chains, and more particularly to hooks used to capture large chain links.
2. General Background
In the offshore industry of drilling for and producing hydrocarbons, a combination of anchors fixed in place in the sea floor, chains, and various types of ropes including wire ropes are used to moor floating platforms, mooring buoys, and vessels in place. Due to the water depths, environmental forces, and size of the floating platforms and vessels the size of the wire, ropes, and chains tends to be very large. As an example, it is not uncommon for the wire, ropes, and chain material to have a diameter of five to six inches. Such large materials require special equipment when performing installation, maintenance, or repair work.
Handling of chains can be accomplished using hooks. The hook typically encompasses the outside of an individual link at one end where it joins with an another link and uses the weight and associated bearing of the adjacent chain links to keep the link in place on the hook. All of the various types of commercially available chain handling hooks follow this general principle. Examples of handling devices are the grab hooks, Devil's Claw, Pelican Hook, and a hook made by British Engines Ltd (to be referred to as a BEL hook).
A grab hook is a conventional hook with the opening narrowed down to capture a given chain link. These hooks only support one side of the captured link.
The Devil's Claw chain stopper straddles either side of a loaded link capturing both sides of the next (load bearing) link. It is not intended to support a span of chain through lateral support of a given link.
The Pelican Hook is designed to capture and support a given chain link in the mid-span of the chain. The pelican hook only bears on one side of the captured link and is secured with a bail to prevent opening and secure the link.
The BEL hook is also designed to capture and support a given chain link in the mid-span of the chain. It also bears only on one side of the captured chain link and can be prone to “chain running” if there is sufficient difference between the load in the chain on either side of the hook.
The known art is lacking in that it supports only one side of the captured link, does not support a span of chain through lateral support of a given link, is only designed to support a given chain link in the mid-span of the chain and requires a moving part such as a bail, or can be prone to chain running.